The present invention relates to the processing of waste material, more particularly processing waste material generated aboard marine vessels.
Environmental regulations have increasingly restricted the discharge of ship-generated wastewaters overboard. It is anticipated that future discharges of untreated blackwater (e.g., urinal and water closet wastes), graywater (e.g., shower, sink, galley, and laundry wastes) and oily wastewater will be prohibited in many areas of the world.
Shipboard liquid wastewater has been generally classified as either non-oily waste or oily waste. The non-oily fractions include blackwater and graywater. Bilgewater and waste oil make up the shipboard oily waste. Blackwater (or sewage) is the waste that is generated by water closets and urinals. Typically, blackwater consists of feces, urine, wipes, and flushing water. Graywater is wastewater generated by sinks, showers, laundry equipment and galley and scullery equipment. Typically, graywater consists of water, dirt, detergents, food particles, hair, lint, and numerous other contaminants.
Bilgewater originates as seal and equipment leaks, condensation, evaporator dumps, and fuel strippings. Typically, bilgewater consists primarily of water (usually greater than 99 percent) with small amounts of fuel oil, lubricating oil, detergents, particulate matter, corrosion products, and other contaminants. Waste oil is a mixture of oil and water separated from the bilgewater. The fraction of water contained in the waste oil can vary by as much as 10 to 90 percent. The fraction of waste oil contains predominantly fuel and lubricating oils (greater than 90 percent of the bulk oil), with smaller amounts of detergent and emulsified water. The bulk oil can have associated therewith a recoverable heating value.
On large ships, current practice involves storing the liquid wastes onboard when the ship is in transit or is moored in restricted waters, until such time as when the liquid wastes can be off-loaded to shore facilities or to a barge. Certain ships are designed to have sufficient storage capacity to retain liquid wastes for a maximum of 6 hours. If suitable off loading facilities are not available, such ship must alter its schedule in order to discharge at sea beyond coastal waters. Other concerns involve the high disposal costs when off-loading liquid wastes to barges, operational security concerns when off-loading to shore facilities in hostile ports, and safety and accidental discharge concerns associated with barging.
As a result of increasingly stringent water quality standards being imposed under state, national, and international regulations, wastewater offload and disposal costs in domestic and foreign ports and harbors continue to increase.
In view of the foregoing, it is an object of the present invention to provide a system for treating liquid wastes aboard ship, thereby obviating the need for discharging ship-generated wastewaters overboard.